1. Field of the Invention
The disclosure is related to an antenna structure.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
An antenna array is composed of a plurality of isotropic radiators. Amplitude and phase difference of radiation are caused by a current flowing through the antenna array. An antenna array exhibits better controllability than a single antenna. Therefore, antenna arrays are suitable for many applications.
For example, a multi-beam antenna array is often used in near-field microwave imaging applications. In the near-field microwave imaging applications, the radiated electromagnetic wave is in a spherical wave and is focused through a lens on a focus plane of an antenna array. To generate an image of larger size, the required curvature of the focus plane becomes greater. Accordingly, the receiving antenna array on the focus plane is required to be rotated to match the adjusted curvature. However, if the focus plane is rotated, not only do the radiation patterns of each array unit interfere with one another, but the layout of the transmission lines of the radio frequency circuit at the back end become extremely complicated, which results in reduced resolution and consumption of a great amount of energy.
Accordingly, there is a need to design an antenna structure which can be arranged as a multi-beam antenna array. The direction of the radiation beam of the antenna structure is configurable, and the noise of the operating frequency can be eliminated. The multi-beam antenna array does not need to be moved or rotated. In addition, the antenna structure can suppress side lobe level to maintain the spatial resolution of the lens.